Environmental stress has direct but complex effects on human health. Phenotypic plasticity in response to environmental stress may result in both adaptations necessary for survival as well as pathologies detrimental to well-being. The model organism Caenorhabditis elegans enters into a stress-resistant 'dauer' stage in response to adverse environmental conditions. The dauer is a classic example of developmental and behavioral plasticity. We previously showed that the dauers undergo extensive and reversible neuronal remodeling in a set of IL2 sensory neurons and that this remodeling is dependent on the furin homolog, KPC-1. During this grant period we will: 1) Extend our investigations into the role of KPC-1 in remodeling by identifying substrates. Furthermore, we will investigate the role of KPC-1 in additional stages of phenotype plasticity in C. elegans. 2) Characterize mutants isolated from a mutagenesis screen that are defective in IL2 remodeling 3) Analyze the ultra-structural properties of the IL2 to uncover the requirements necessary for their inherent plasticity.